Historical Imagery of Greenland Glaciers Lessens Sea Level Rise Alarm

A new study using historical images of glaciers in southeast Greenland to investigate glacier response to climate changes suggests that the recently observed acceleration of ice loss from Greenland may not be a long-term phenomenon. Instead, as marine terminating glaciers reach their grounding line and as the termini of land-terminating glaciers migrate upwards in elevation, ice loss rates from glacial discharge may slacken. According to Anders Bjørk and co-researchers:

[T]he recent high rate of retreat may come to a slowdown when retreating marine-terminating glaciers reach their grounding line and become less sensitive to the influence of ocean temperature, or through positive or negative feedback mechanisms relating to the cold East Greenland Coastal Current.

and,

Our results have implications for future estimations of sea-level rise as retreat rates for marine-terminating glaciers are likely to increase as temperature rises until glacier fronts reach the grounding line, or when cold ocean currents re-establish, whereas retreat rates for land-terminating glaciers are not likely to rise in the same order of magnitude.

Such results throw a bit of cold water on alarmist ideas that rising temperatures will lead to ever-accelerating ice loss from Greenland and accelerating sea level rise.

For example, Eric Rignot and colleagues (2011) last year documented an acceleration in the rate of ice loss from Greenland (and Antarctica) over the past two decades. They extrapolated this acceleration into the future, to arrive at potential future sea level contributions from the loss of ice sheets:

At the current rate of acceleration in ice sheet loss, starting at 500 Gt/yr in 2008 and increasing at 36.5 Gt/yr2, the contribution of ice sheets alone scales up to 56 cm [22 in.] by 2100.

Rignot et al. (2011) were quick to note that this rather naïve extrapolation was probably less than reliable:

While this value may not be used as a projection given the considerable uncertainty in future acceleration of ice sheet mass loss, it provides one indication of the potential contribution of ice sheets to sea level in the coming century if the present trends continue.

The new Bjørk et al. (2012) study (as well as a slew of other recent studies which we have discussed: see here, here, here, here, here , and here for example) strongly suggests that “present trends” will not continue—and thus the Rignot et al. extrapolation is grossly inaccurate (i.e., far too large).

Bjørk and colleagues came to their conclusion by studying some recently unearthed historical photographs of the coast of southeastern Greenland that had been taken by early 20th century Danish expeditions to the region. The earliest photos were from the early 1930s. Combining those photos with a set of U.S. WWII military photos and modern satellite imagery, Bjørk and fellow researchers were able to build a photographic database of the behavior of the glaciers in the region for much of the 20th and early 21st centuries, and related that behavior to climate changes observed across southeast Greenland.

They found that the glaciers respond rather quickly to climate changes. The well-known warmth of the region during the early 20th century was accompanied by relatively rapid retreat of both marine-terminating and land-terminating glaciers. As temperatures cooled from the 1950s through the 1980s, many glaciers advanced, and the warming of the past two decades has again been marked by rapid glacier retreat (Figure 1).

Figure 1. Behavior of glaciers along Greenland’s southeastern coast during different periods during the past 80 years. Glaciers generally retreated during the relative warmth of the 1930s-1940s and again in the early 21st century. Some glacier advancement was observed during the relatively cool conditions of the 1960s-1970s. (source: Bjørk et al., 2012)

This pattern of behavior of glacial dynamics is exactly like that of surface ice melt in Greenland that we documented in our paper (Fraunfeld et al., 2011) from last year and discussed here. In that paper, we concluded the following:

The forces acting in concert with ice melt across Greenland to produce higher global sea levels currently, should also have been acting during the extended high‐melt conditions from the mid‐1920s to the early 1960s. There is some qualitative indication of an observable influence of the variations in input from Greenland in the decadal rates of sea level change over the course of the past century… However, there is no indication that the increased contribution from the Greenland melt in the early to mid 20th century, a roughly 40 year interval when average annual melt was more or less equivalent to the average of the most recent 10 years (2000–2009), resulted in a rate of total global sea level rise that exceeded ∼3 mm/yr. This suggests that Greenland’s contribution to global sea level rise, even during multidecadal conditions as warm as during the past several years, is relatively modest.

The implications of the new results reported by Bjørk at al. are in accordance.

Bjørk at al. note that in the early 20th century warmth, both marine- and land-terminating glaciers increased their rates of retreat, but during the relative warmth of the early 21st century, the marine-terminating glaciers retreated at a greater rate than the land-terminating glaciers. They speculated that the reason the land-terminating glaciers did not respond as much to the recent warmth was that they had retreated to higher elevations during the warmth of the early 20th century and thus were less sensitive to further warming. Bjørk et al. further speculated that even though the marine-terminating glaciers may continue their increasing rate of retreat with further ocean temperature increases, that this increase will not continue indefinitely, but will begin to slow as the marine-terminating glaciers reach their grounding line. Together, their results indicate the potential for only modest increases in the annual amount of ice loss as condition warm (similar to our findings reported above).

Currently, ice loss from Greenland contributes about one-to-two hundredths of an inch per year to the global average sea level—that’s a total of 1-2 inches by the year 2100. So, even if the rate of ice loss doubles or triples, the resulting sea level rise falls far short of being catastrophic. And the more evidence that comes in, the more confidence we have that as temperatures rise, Greenland will shed ice only gradually and through somewhat self-limiting processes—rather than catastrophically through rapid acceleration and “slipping into the sea” as Al Gore so indelicately described his (incorrect) vision of the future.

” And the more evidence that comes in, the more confidence we have that as temperatures rise, Greenland will shed ice only gradually and through somewhat self-limiting processes—rather than catastrophically through rapid acceleration and “slipping into the sea” as Al Gore so indelicately described his (incorrect) vision of the future.”
Before the “was it peer reviewed?” trolls jumps all over this, here is what I have to say….

On several occasions over the last few years I’ve mentioned this in the context of the “easy ice” notion. It is not really complicated. For example, about one year ago on P. Gosselin’s NoTrickZone:http://notrickszone.com/2011/06/23/leading-german-meteorologist-michael-manns-sea-level-story-a-quack/#comments
quote. . .
Although there are other possibilities it seems the notion of sea level rise is based on the assumption of ice melting somewhere or everywhere that is not already floating. But, the easy ice has already melted. For example, the Puget Lobe during the Vashon Stade (Fraser Glaciation) is estimated to be a few thousand feet thick in the area of Seattle, WA. with the ice mass depressing the region well below today’s sea level. Relatively speaking this area is closer to the tropical area and gets higher sun than places, say, in Alaska, Greenland, or Antarctica. This combination of factors caused rapid melting – when the glacial event ended (for whatever reason). Today remaining ice, because of high elevation and/or high latitude, will be more difficult to melt. It seems to me that if one is looking for an increase in sea level from melting ice – expect it to be slow and slowing or easily reversed. Other contributions to sea level change are many and complicated.
. . .unquote

As for extrapolations and such, remember what Mark Twain said:
“In the space of one hundred and seventy-six years the Lower Mississippi has shortened itself two hundred and forty-two miles. That is an average of a trifle over one mile and a third per year. Therefore, any calm person, who is not blind or idiotic, can see that in the Old Oolitic Silurian Period, just a million years ago next November, the Lower Mississippi River was upwards of one million three hundred thousand miles long, and stuck out over the Gulf of Mexico like a fishing-rod. And by the same token any person can see that seven hundred and forty-two years from now the Lower Mississippi will be only a mile and three-quarters long, and Cairo and New Orleans will have joined their streets together, and be plodding comfortably along under a single mayor and a mutual board of aldermen. There is something fascinating about science. One gets such wholesale returns of conjecture out of such a trifling investment of fact.”
– Life on the Mississippi

This comes as no surprise. The historic record of Greenland temperatures from a number of weather stations shows that temperatures were higher and rose at a faster rate in the 1930s than the warming of 1978-1998. Isotope data from the GISP2 ice core confirm 20 warm periods and 20 cool periods since 1480–the ice sheet waned during the warm periods and waxed during the cool periods. Nothing new here–it’s been going on for thousands of years.

in 1942 a flight of planes was forced to land on the greenland icecap just inland from the southeast coast…they were found in 1992…one was recovered, repaired and flown…a P-38 named Glacier Girl….the planes were under 268 feet of ice…would anyone care to extrapolate and figure out how much the icecap would grow by 2100?

I wonder if the historical temperatures got as hot in Greenland as it’s getting right now.
“The record books for Greenland’s climate were re-written [last] Tuesday, when the mercury hit 24.8°C (76.6°F) at Narsarsuaq, Greenland, on the southern coast. According to weather records researcher Maximiliano Herrera, this is the hottest temperature on record in Greenland for May, and is just 0.7°C (1.3°F) below the hottest temperature ever measured in Greenland. The previous May record was 22.4°C (72.3°F) at Kangerlussuaq (called Sondre Stormfjord in Danish) on May 31, 1991. The 25.2°C at Narsarsuaq on June 22, 1957 is the only June temperature measured in Greenland warmer than yesterday’s 24.8°C reading. Wunderground’s extremes page shows that the all-time warmest temperature record for Greenland is 25.5°C (77.9°F) set on July 26, 1990.”

Don Easterbrook says:
June 4, 2012 at 10:30 pm
…….
You are absolutely correct . If one looks at page 20 of the paper it is obvious that the temperatures quoted are directly correlated with the AMO, which is historically high, currently is at peak of its 65 year cycle, which goes back to 1700s, although sequence was broken in the Dalton min time.
The AMO is about to turn down, as its precursor the northern leg of the NAO shows with some years delay.
The AMO and NAO run synchronously until about 1910, and then the North Hemisphere temperature took off, and the NAO’s speeded up, while the AMO carried with its 9.1 and 65 year cycles. It is a bit odd, but should be of some interest, that if you squeeze the AMO it falls again into a perfect synchronism with the NAO.http://www.vukcevic.talktalk.net/AMO-NAO.htm
There is perfectly good natural reason for it, but climate people are more interested in puny radiative constants than essentials of the natural climate variability

Currently, ice loss from Greenland contributes about one-to-two hundredths of an inch per year to the global average sea level—that’s a total of 1-2 inches by the year 2100.
And of course this is part of the 7 – 8 ” per century seen since 1900.

Currently, ice loss from Greenland contributes about one-to-two hundredths of an inch per year to the global average sea level—that’s a total of 1-2 inches by the year 2100.
And of course this is part of the 7 – 8 ” per century seen since 1900. (Homewood)
At the risk of being overly pedantic, IF that number is true (I think it’s Bull – Excrement, myself!)
over 1/2 of that occurred well before CO2 rose significantly after the 1960’s. SO, “go fish”…I mean that “politely”. I.e., fish for a BETTER REASON than CO2…

This is not new news. The earlier 1920s warming of Greenland is well known.
See: Current Melting Of Greenland’s Ice Mimicks 1920s-1940s Event, ScienceDaily (Dec. 10, 2007), http://www.sciencedaily.com/releases/2007/12/071210094332.htm
This shows how sensitive Greenland’s glaciers are to changes in climate. The climate change of 1920s was regional. The current climate change is global.

Mike says:
June 5, 2012 at 9:10 am
From your link:… Their evidence reinforces the belief that glaciers and other bodies of ice are exquisitely hyper-sensitive to climate change …
Funny that,solid ice changing state to liquid water all at exactly the same temperature.
I predict that seas close to boiling will be exquisitely hyper-sensitive to changing to steam. Funny that.

Mike says
This shows how sensitive Greenland’s glaciers are to changes in climate. The climate change of 1920s was regional. The current climate change is global.
———————————————————————————————————————
but if you take away all the ADJUSTMENT made to the global temp record you are left with
a 0.4c rise.
could you point out some current climate change please?

Of course Ice-loss is not a long-term phenomenon.
Glaciers are just snow staying through the summer.
If there is more snow in winter, and it gets colder in summer, ice will start to accumulate.
The notion of glacier “tipping points” must rest on a belief that glaciers are a million years old, and therefore it must take a million years to make one.
Not so!
It takes 1 year to make a glacier from nothing, and it takes 1 year to make a polar ice-cap from nothing. Flimsy at first, but in just a few years you get impressive results.
Please do not worry about the health of glaciers or sea-ice. They are products of a combination of snow and cold weather. Whenever these two conditions are present, they will start to accumulate, and very quickly indeed.

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